The present invention is directed to glazing, such as automotive and architectural glazing, and the like, having a solar control coating on a surface of a substantially transparent substrate. More particularly, the present invention is directed to thermostable glazing having a thermostable solar coating on such substrate for anti-solar properties, as well as to methods of manufacturing such thermostable glazing.
Coated glazing products having anti-solar properties, that is, low transmittance of wavelengths in the infra-red range, are known to those skilled in the art. Also, low emissivity coatings for glazing products are disclosed, for example, in European patent application 0,104,870 to F. H. Hart entitled Low Emissivity Coatings On Transparent Substrates. That document discloses low emissivity silver coatings comprising a layer of silver and an overlying anti-reflective layer of metal oxide. Cathodic sputtering is disclosed for producing such low emissivity coatings having a small amount of an additional metal dispersed non-uniformly in the silver layer. Sputter deposition of a multi-layer, low emissivity coating is described, for example, in European Patent Application 0,418,435 to Nalepka. Similarly, a multi-layer low emissivity coating is disclosed in European patent application 0,418,435 to Hayward et al. The multi-layer coating of Hayward et al. is said to comprise a layer of sputtered zinc, tin, titanium, indium/tin or bismuth oxide, next a layer of sputtered silver or silver alloy, then a layer of sputtered titanium or stainless steel and finally a layer of zinc, tin, titanium, indium/tin or bismuth oxide. Such multi-layer film is said to have excellent visible light transmission while controlling both near infra-red solar energy and far infra-red reflected energy. A temperable coated article is suggested in U.S. Pat. No. 5,552,180 to Finley et al. The coated article of Finley et al. employs a metal-containing film such as titanium nitride which ordinarily oxidizes at the high temperatures encountered during glass tempering, along with an overcoating of a protective layer of a silicon compound and an undercoating with a stabilizing metal-containing layer. In U.S. Pat. No. 3,990,784 to Gelber a multi-layer coating for architectural glass is suggested, comprising first and second metal layers with a dielectric layer disposed between them. Gelber suggests that the transmission properties of the coating can be changed independent of its reflection properties, by varying the thickness of the metal layers while maintaining the ratio of their thicknesses constant.
In general, conventional low emissivity coating systems employ a first dielectric film or layer directly on a surface of a transparent substrate, followed by metal film and then a second dielectric film over the metal film. Where the metal film employs silver or other easily oxidized metal, a buffer film typically is positioned between the metal and the second dielectric films. The buffer film substantially inhibits migration to the metal film of oxygen or other reactive gas employed in the deposition of the second dielectric film. Conventional dielectric materials include, for example, oxides such as zinc oxide, tin oxide, zinc/tin oxide composites, indium/tin oxide, bismuth oxide, titanium oxide, etc., and nitrides such as tin nitride. Co-pending application U.S. Ser. No. 09/098,316 (Demiryont et al.) discloses a multi-layered coating in which tungsten oxide is employed as a dielectric material. The metal layer may be formed of silver, although other metal layers also are known to those skilled in the art. Suitable buffer layers for protecting a silver or other metal film have typically included, for example, a film formed of sub-oxide of chrome or chrome/nickel or nitride of silicon or titanium with a thickness of, e.g., 15 xc3x85 to 60 xc3x85. The thickness of the metal film is selected to provide adequately low emissivity while maintaining sufficiently high transmittance of visible light to meet the requirements of the intended application. The thickness of the bottom and top dielectric films is selected typically to achieve adequate anti-reflectance for the metal film, whereby the entire multi-layer coating has improved transparency to visible light.
Various difficulties have been encountered by those skilled in the art in developing commercially suitable coatings for architectural and automotive glazing. Both architectural and automotive applications require materials able to withstand applied force, e.g., as caused by pressure or temperature gradients between the internal and external surfaces, changes in load resulting from building sway, road vibration, wind or direct impact Typically, window glass employed in vehicles or buildings is xe2x80x98temperedxe2x80x99 or xe2x80x98annealedxe2x80x99, a strengthening process which entails exposure to high temperatures followed by gradual cooling. In glazing for automobiles or trucks, such heating may also be required for bending the glazing (e.g., a windshield, sunroof or other view panel) into a desired shape. Prior art coatings cannot adequately withstand exposure to the high temperatures required for such bending or other heat treatment of a glass substrate, e.g., 570xc2x0 C. to 610xc2x0 C. for bending and 600xc2x0 C.-650xc2x0 C. for tempering soda-lime-silica glass, unless thermally shielded , e.g., by a protective layer such as a metal layer. That is, they would lose their characteristic solar control optical properties upon exposure to such thermal tempering, and therefore, such prior known solar coatings must be applied after tempering or shaping of the glass substrate. This is particularly disadvantageous in the coating of bent or curved glazing, since specialized equipment must be used in order to apply a coating to a non-flat surface. There is, therefore, need in this technology area for heat-stable or thermostable solar coating in order to allow the easy and inexpensive coating of stock, flat xe2x80x98blanksxe2x80x99 of glass or other transparent glazing material using standardized coating equipment, such that coated material may be produced and stored for future custom processing (i.e. tempering and/or bending).
There has long been need in the glazing industry for a solar coating which can be uniformly deposited by D.C. magentron sputtering onto large surface areas with fast deposition rates, low deposition power density, good film quality, including high film durability and long shelf life. As used here, large area deposition refers to deposition onto transparent substrates suitable in size for architectural and automotive glazing applications. Fast deposition rate is desirable, since it can reduce the time and cost of producing the coated articles. Long lasting source material to deposit reproducible films also is desirable. Low deposition power density is desirable both to reduce the cost of energy employed in manufacturing the coated article and to provide more uniform coating thickness and density. The reference here to a coated substrate having long shelf life is intended to mean, especially, that the coated surface can be exposed to air for hours or even days without substantial degradation of film quality, for example, due to migration of oxygen or moisture from the air into the coating to react with the coating materials. In that regard, in prior known manufacturing processes substantial production wastage occurs when a coating on a glazing panel deteriorates significantly if it is not immediately laminated or otherwise assembled into a multi-pane window which protects the coating from exposure to air. Increasing the time period during which a coated glazing panel can be stored prior to being laminated or assembled in this fashion provides significant production flexibility and consequent reduction in processing cost and complexity.
It is an object of the present invention to provide thermostable glazing meeting some or all of these long-felt industry needs. In particular, it is an object of at least certain preferred embodiments of the invention to provide thermostable glazing comprising a substantially transparent substrate with a substantially transparent solar coating on a surface of the substrate, which coating has high film durability, long shelf life, and can additionally withstand post-deposition heat treatment at the substrate""s bending and tempering temperatures.
It is a further object of the invention to provide methods of manufacturing the aforesaid thermostable glazing.
Additional objects and advantages of the present invention will be readily understood by those skilled in the art given the benefit of the following disclosure of the invention and detailed description of certain preferred embodiments.
In accordance with a first aspect of the invention, thermostable glazing comprises a substantially transparent substrate with a substantially transparent thermostable solar coating on a surface of the substrate. The thermostable solar coating is formed of copper oxide. In accordance with preferred embodiments, the thermostable glazing unit has visible transmittance ranging between 5% and 50% and comprises a substantially transparent substrate with a substantially transparent, thermostable solar coating on a surface of the substrate. The substantially transparent thermostable coating is formed of copper oxide, as disclosed above. Optionally, the CuOx solar coating is combined with other coating layers, for example, an anti-reflection coating layer, a coloration coating layer, etc., which also are thermostable, in an integrated coating on the surface of the glazing substrate. The term xe2x80x9cintegrated coatingxe2x80x9d means an optical coating in accordance with the present disclosure, wherein the thermostable solar coating has not only the copper oxide layer, but also at least one other coating layer lying directly over or under the copper oxide layer. An integrated coating in accordance with certain preferred embodiments, for example, may have an anti-reflection layer deposited directly on the surface of the substrate prior to deposition of the copper oxide thermostable coating, such that the anti-reflection coating layer is sandwiched between the glass substrate and the copper oxide layer: The copper oxide layer and the anti-reflection layer together in such embodiment form one integrated coating on the substrate surface.
A xe2x80x9csolar coatingxe2x80x9d as that term is used here, is a substantially optically transparent coating which reduces transmittance of total solar energy through a glass or other pane which carries the solar coating, by at least about 5%, preferably 5% to 50%, for example, about 15%, as measured by a Perkin Elmer Model Lambda 900 UV-Vis-Near IR spectrophotometer. Performances of the coating are calculated by a standard Window 4.1 program prepared by LBL Window and Daylight Group for the U.S. Department of Energy. Film thicknesses are measured by a Tencor Model Alpha step 500 thickness measuring apparatus. Mechanical properties of the samples are determined by a Taber Abraser machine. Environmental stability of the samples are evaluated by using a whedering cabin controlling ambient temperature and humidity. The solar coatings disclosed here are substantially transparent to visible light, preferably having at least about 10% transmittance, more preferably at least 20% transmittance, as measured by a spectrophotometer.
The solar coatings disclosed here are thermostable in that, when subjected to thermal stress, they are resistant, against degradation, most notably in their capacity to block or transmit light. In addition, the term xe2x80x9cthermostablexe2x80x9d refers to a coating or coated article of manufacture which substantially retains its characteristic mechanical properties, such as body integrity, surface continuity, tensile strength and adhesiveness (e.g., between coating and substrate). The term xe2x80x9cthermal stressxe2x80x9d is herein taken to mean the stresses encountered upon exposure to high temperatures used for heat treatment, e.g., for tempering or bending the glazing substrate. Typically, such temperatures are in the range of 590xc2x0 C. to 650xc2x0 C. The solar coatings of the invention are thermostable at the tempering temperature of the glazing substrate and/or at its bending temperature.
Preferably, the copper oxide coating is directly on the surface of the substrate. The copper oxide layer forming the thermostable solar coating of the present invention, particularly if used as a mono-layer or single coating (that is, directly on the surface of the substrate with no other coating layers of other materials), preferably has a substantially uniform film thickness of about 150 xc3x85 to 3000 xc3x85, more preferably about 1000 xc3x85 to 2000 xc3x85. For example, when used on 5 mm thick soda-lime-silica glass for a so-called xe2x80x9cmoon roofxe2x80x9d in a motor vehicle, a thermostable solar coating formed of a mono-layer of copper oxide without any other adjacent coating layers, preferably is about 1200 xc3x85 mm thick. When used with auxiliary coating layers, that is, layers of other materials in the same film stack, the copper oxide layer may be the same because optical performance of the solar coating is mainly controlled by the CuOx film.
As used herein, in reference to a substantially transparent substrate used in the invention or a coated article of the invention, the term xe2x80x9ccolorxe2x80x9d refers to that which, when held up before the eye of an observer, causes the spectrum of visible light seen by the observer to be noticeably altered.
As used here and in the appended claims, the substantially transparent, thermostable coating is said to be xe2x80x9cdirectly onxe2x80x9d or to xe2x80x9cdirectly overliexe2x80x9d the substrate if no other material or coating is positioned between them. In this regard, the coating may be said to lie directly on the substrate notwithstanding that there may be a slight transition zone between the them, involving migration of the material of the coating into the substrate and/or interface reaction products different from the primary composition of the substrate and the coating.
In preferred embodiments the substantially transparent substrate is a flat or curvo-planar pane of glass, glass ceramic, plastic or glass-plastic composite. It is highly preferred that the substantially transparent substrate be a panel of a glass selected from the group consisting of soda-lime-silica glass, borosilicate glass, aluminosilicate glass, vycor, fused silica and vitreous silica. It is particularly preferred that the glass be soda-lime-silica glass.
Optionally, the transparent glazing substrate has color. The color of an article of manufacture of the invention (i.e. before and after heat treatment) are calculated using the Commission Internationale de L""Eclairage (CIE) color difference equation:
E=[(L*)2+(a*)2+(b*)2]xc2xd
where a*, b* and L* are color coordinates in CIE uniform color space. According to certain preferred embodiments, the glazing substrate is a panel of body-colored glass. The term xe2x80x9cbody-colored glassxe2x80x9d refers to glass which, in the form of a pane as used in the present invention, imparts optically perceptible color to sunlight viewed through the glazing along a line of sight substantially normal to the plane of the glass. The color is optically perceptible if it is perceptible to the unaided human eye. Glazing substrates suitable for the present invention, such as soda-lime-silica glass, can be given body color by incorporating any of numerous suitable colorance materials, such as iron oxides, e.g., CoOx, CrOx, and MnoX. Given the benefit of this disclosure, numerous other suitable colorants and suitable amounts thereof will be readily apparent to those skilled in the art without undue experimentation. It should be recognized that such colorants and other suitable additives to the glass composition can contribute to the solar management properties of the glass. For example, iron-oxides can reduce transmittance of infrared and ultraviolet light. Thus, in accordance with certain preferred embodiments, thermostable glazing is provided which has a copper oxide coating, as disclosed above, along with body colorant materials in the glass for further reduction of UV and IR light, etc., without undue or unacceptable reduction of visible light transmittance. In that regard, it will be recognized by those skilled in the art that surface conditions and interfacial conditions may exist in the thermostable glazings disclosed here, without departing from the invention. For example, residuals from fining aids and/or other processing materials added to the glass during its manufacture, and for example, reaction products and/or migratory materials resulting from the xe2x80x9cflutexe2x80x9d process used to prepare typical glass substrates, may exist in the thermostable glazings of the invention and may contribute coating disclosed here, for example, during the coating process and/or during subsequent heat treatment of the coated glazing. All such residuals, migration and reaction products are meant to be included by implication in the thermal glazings disclosed and described here, and likewise, included by implication in the products and processes defined in the appended claims. According to other preferred embodiments, the glazing has a color control layer. Preferably, the color control layer has a thickness less than 700 xc3x85 and comprises material selected from thermostable oxides or nitrides, e.g., SnO2, WO3 and Si3N4. It is preferred that the color control layer lies directly over or under the copper oxide layer of the solar coating.
As noted above, certain preferred embodiments of the invention further comprise an anti-reflection layer. Preferably, any such anti-reflection layer forms an integrated coating with the copper oxide thermostable solar coating. Suitable materials for an anti-reflection coating layer include, for example, WO3, SnO2 and Si3N4. Such anti-reflection layers typically have a thickness of approximately 50 xc3x85 to 2000 xc3x85, more preferably 200 xc3x85 to 1000 xc3x85, for example, 400 xc3x85. Other suitable anti-reflection materials and thicknesses will be readily apparent to those skilled in the art given the benefit of this disclosure. Furthermore, it will be understood from this disclosure by those skilled in the art, that any such anti-reflection layer, color control layer and/or other coating layers included in an integrated coating with the copper oxide thermostable solar coating should also be substantially thermostable. That is, they should be at least sufficiently thermostable that they can withstand heat treatment of the substrate, such as tempering or bending, and contribute the desired optical properties, two of the glazing product after such heat treatment. Typically, in preferred embodiments, the copper oxide layer employed in the thermostable solar coating and any other coating layers preferably have substantially uniform film thickness. The term xe2x80x9csubstantially uniform film thicknessxe2x80x9d and like expressions used here are intended to mean uniform to the degree needed for the intended purpose of the coating. In that regard, those skilled in the art will recognize that certain tolerable variations in film thicknesses occur naturally, including color for example, variations in film thickness between the center and the edges of a coated substrate.
In accordance with another aspect, methods are provided for making the thermostable glazing disclosed above. Such methods comprise providing a substantially transparent substrate, typically with appropriate surface preparation steps being performed on the surface to be coated. Typically, cleaning of the substrate is the first step prior to deposition. The thermostable solar coating is then formed on the surface of the substrate by depositing a layer of CuOx. The CuOx solar coating can be deposited directly onto the surface of the substrate. In alternative embodiments, the method further comprises the step(s) of depositing a coloration coating layer for color control of the glazing, and/or an anti-reflection coating layer and/or other thermostable coating layers to form an integrated coating on the substrate surface with the CuOx solar coating. It is preferred that the step of depositing the coloration coating layer comprises sputtering a material selected from WO3, SnO2 and Si3N4 and the like to a thickness of about 600 xc3x85. Preferably, the method further comprises the steps of washing and substantially drying the surface of the substrate.
In accordance with preferred embodiments, the substantially transparent copper oxide solar coating of the present invention is deposited by sputtering in one or a series of sputter stations arranged sequentially in a single sputtering chamber through which the transparent substrate passes at constant travel speed. Suitable partitions, such as curtains or the like, separate one sputter station from the next within the sputtering chamber, such that different deposition atmospheres can be employed at different stations. A reactive atmosphere comprising oxygen can be used, for example, at a first station to deposit the copper oxide solar coating.
D.C. Magentron sputtering has been utilized for the deposition of metals and some metallic oxides (e.g., SnO2, Bi2O3, ZnO and, in the above-referenced copending application, tungsten oxide); however, the large-area deposition of CuOx as an optical coating is a novel process. Sputtering of CuOx onto glass produces a brown film which is stable after heat treatment, e.g., at 635xc2x0 C. Such CuOx films are far more durable than sputtered tin films, even when a heat-treated CuOx-coated object is compared to a tin film which has not undergone thermal stress. A single-layer CuOx solar coating exhibits transmittance which is inversely proportional to film thickness. Thus, a graded series of thicknesses ranging from 220 xc3x85 to 1500 xc3x85 produces a corresponding series of film transmittances ranging between 40% and 11%. It is preferred that the substantially transparent substrate is soda-lime-silica glass and the method further comprises the step of tempering or otherwise heat treating the substrate.
In accordance with certain highly preferred embodiments of the manufacturing method disclosed here, the substantially transparent thermostable coating is deposited by multiple passes, preferably two passes through such multi-station sputtering chamber. Repeating of deposition means increasing the film thickness by multi-pass of the substrate under the depositing target, so the visible light transmittance is reduced. During each of the passes through the sputtering chamber, a layer is deposited comprising copper oxide. Thermostable optical coatings formed in accordance with such multi-pass methods of the invention are found to have substantially improved coating properties, including especially to form a pin-hole free coating. Pinhole free coatings are very important for longer life time and better film quality/durability. It will be within the ability of those skilled in the art, given the benefit of this disclosure, to achieve both enhanced uniformity and desired hue or color of the coated article. Reference here to uniformity of color refers to reduction in blotchiness or the like which may otherwise appear in a coated article.
The thermostable solar coating of the invention substantially retains its reflective and refractive properties after post-deposition heat treatment. A sheet of substrate material may, after coating, be subjected to temperatures suitable for bending or tempering without substantial degradation of reflectance or transmittance properties. Bending of a typical sheet of architectural or automotive glass (e.g., a 4 mm thick sheet of soda-lime glass) requires 15 minutes heating to 550xc2x0 C. and then for approximately 2 minutes to 600xc2x0 C. for bending and then cooling over a 15 minute time period to room temperature after bending. To produce tempered glass, a glass substrate is heating to approximately 635xc2x0 C. and then subjected to surface chilling, such that the material cools to room temperature within two minutes and is compressed relative to the untempered material. This compression results in enhanced performance of the glass when it is under mechanical stress.
It will be apparent to those skilled in the art in view of the present disclosure, that the present invention is a significant technological advance. Preferred embodiments of the substantially transparent, thermostable, dual-function coatings disclosed here have excellent performance characteristics, including advantageously high anti-solar properties, that is, high attenuation levels of direct solar radiation. The above-disclosed copper oxide coating is a novel coating which is highly suitable for large area deposition by sputtering and which allows a coated substrate of standard composition and dimensions to be heat-treated for strength and/or fashioned into any desired shape after months, or even years, of storage. Fast deposition rates can be obtained with copper oxide, even employing advantageously low deposition power densities. In addition to the high durability and long shelf-life of the coating of the invention, copper is inexpensive relative to metals used in solar-control coatings of the prior art and deposition of the coating layers may be performed at room temperature, obviating any need for controlled-temperature sputtering chambers. It is particularly advantageous that the copper oxide layer can be formed by reactive sputtering from a pure copper target with little or no target poisoning.
The copper oxide coating of the present invention has a high refractive index similar to amorphous Si, being about 3.5 in the mid-visible wavelength range. The copper oxide, solar coatings disclosed here provide desired spectral performance characteristics at thicknesses less than that required for other known solar coatings, such as CoOx and CoOxxe2x80x94FeOx which are known pyrolytic privacy coatings for automotive windows. Although these privacy glasses are temperable and good for side windows, the pyrolytic coatings cannot reach the desired low visible transmittance (10%-15%) because of their limited coating thicknesses. The thickness of the CuOx layer of the present invention can be controlled by selecting a suitable number of passes through the sputter deposition chamber, or by adjusting the travel speed of the glass under the spatter targets during deposition. Deposition of the copper oxide layer employed in the coatings disclosed here can be accomplished faster and more economically. As noted above, faster production speeds can yield corresponding reductions in production costs. In addition, the high density of the copper oxide anti-reflection layer employed in the thermostable coatings disclosed here, which is found to be as high as bulk value or nearly bulk value results in long shelf like and excellent durability.
In addition, the copper oxide anti-solar layer has an advantageously low absorption coefficient in the visible and infra-red regions, together with an advantageously high refractive index. The optical properties of the CuOx films are essentially the same as those of Si films; refractive index is 3.5 and extension coefficient 0.03. Table I gives process parameters of CuOx films vs. resulting film properties e.g., film thickness, Tvisible/Ttotal solar for single pain and double pain glass (6 mm clear float glass and 6 mm-12 mm air-6 mm for double pain). Table II is the optical performance table of the some typical samples. In short, the copper oxide layer of the thermostable, anti-solar coatings disclosed here has advantageous thermal and spectral properties, robust deposition properties and excellent mechanical film properties.
Additional features and advantages will be further understood in view of the following detailed description of certain preferred embodiments.